This invention relates to an epoxy resin composition used for the fabrication of a heat-resistant printed circuit laminate.
Necessitated by the trends in electronic packaging characterized by light weight and small size, the requirements in performance of laminates for printed circuit boards such as heat resistance, dimensional stability and mechanical workability are getting harsher. Various epoxy resin compositions have been developed for the fabrication of printed circuit laminates with improved heat-resisting characteristics, dimensional stability and workability. Standard FR-4 laminate is a well known printed circuit board laminate which is now not accessible to modern techniques, such as Surface Mount Technology (SMT). FR-laminate has higher heat resisting characteristics according to NEMA specifications, but is found to be difficult to process due to its high crosslinking density. The glass transition temperatures of these laminates are about 150-160 deg C. Since the laminates for multilayer printed circuit boards are generally manufactured through a hot pressing process at about 180 deg C., the above known laminates especially those having fine lines in inner layers of the boards are usually prone to destruction during the lamination process.
Prior arts described the preparing of epoxy resins by reacting epichlorohydrin with hydantoin or barbituric acid. The resins thus obtained contain a fatty amine which includes heterocyclic groups and exhibit good electrical properties, good water-resistance, and good thermal or dimensional stability. U.S. Pat. No. 4,071,477 discloses a hydantoin based epoxy resin which has good water resisting properties. U.S. Pat. Nos. 3,542,803, 3,592,823 and 3,975,397 disclose epoxy resins containing binucleus hydantoin, and exhibit good water-resistance. U.S. Pat. No. 4,672,101 discloses a compound having a glass-transition temperature greater than 240 deg C., which is prepared by reacting a hydantoin-based epoxy with diamino diphenyl sulfone. U.S. Pat. No. 4,459,392 discloses an epoxy resin prepared from hydantoin and barbituric acid. The mechanical strength and dimensional stability of a polyester resin can be improved when it is blended with the epoxy resin disclosed in U.S. Pat. No. 4,459,392. U.S. Pat. No. 3,779,949 discloses a high molecular weight epoxy resin with a long pot-life and good weather fastness, which is prepared by reacting an epoxy resin with a binucleus heterocyclic compound as a chain extender.